Doesn’t that mean private non-routable subnets like 10.x or 192.x have always been a hack?
Private addresses don't necessitate NAT. IPv6 also allows private addresses in the form of fd00::/8, like fd00:face:b00b:1::1.
No, because there's use cases for systems that aren't connected to the internet. Also, public IPs can be dynamic, so you might not want to rely on them internally.
Doesn’t that mean private non-routable subnets like 10.x or 192.x have always been a hack?
Private addresses don't necessitate NAT. IPv6 also allows private addresses in the form of
fd00::/8, likefd00:face:b00b:1::1.No, because there's use cases for systems that aren't connected to the internet. Also, public IPs can be dynamic, so you might not want to rely on them internally.